Pythium SPP in roots of wheat and rye-grass in Western Australia and their effect on root rot caused by Gaeumannomyces graminis var. tritici

Pythium acanthophoron, P. echinulatum, P. irregulare, P. vanterpoolii, P. vexans, P. violae and a Pythium sp. (unidentified) were isolated from wheat and rye-grass roots. Pythium spp were isolated at a higher frequency at seedling and tillering stages than at other stages of sampling. A greater proportion of these were obtained on potato dextrose agar than on the same medium with lactic acid or streptomycin.

P. irregulare, P. violae and P. vanterpoolii were pathogenic to wheat and rye-grass in sterilized and non-sterilized soil, and with the exception of P. vanterpoolii on rye-grass, reduced their fresh shoot and root weights. P. acanthophoron, P. echinulatum, P. vexans and the Pythium sp. were non-pathogenic to wheat and rye-grass. P. vexans and Pythium sp., however, increased the fresh shoot and root weights of wheat and rye-grass in sterilized and non-sterilized soil.

P. irregulare, P. violae and P. vanterpoolii increased the percentage mortality of wheat and rye-grass resulting from infection by Gaeumannomyces graminis var. tritici in sterilized and non-sterilized soil, with the exception of P. vanterpoolii on rye-grass. P. vexans, the Pythium sp. and P. echinulatum reduced the percentage mortality of wheat and rye-grass resulting from take-all in both soil treatments.